1. Field of the Invention
This invention relates to photographic lighting apparatus and has particular reference to an improved multiflash unit of compact size that contains a plurality of flashlamps.
2. Description of the Prior Art
Disposable multiflash units which contain a plurality of flashlamps that are mounted on a carrier or base member that has an integrally-formed jack holder or post adapted to permit the unit to be inserted into the socket of a camera or into an adapter that is coupled to a camera, are well known in the art. In the so-called "Magicube" flash units presently being marketed, four mechanically ignitable flashlamps are mounted on a plastic base member in operative relationship with a corresponding number of springs for igniting the lamps and a reflector component that defines individual reflector elements for each lamp. The base member is of generally square configuration and a cover of transparent plastic and cubical configuration is fastened to the base member and protectively closes the lamps, igniter springs and reflector component.
The aforementioned Magicube flash units of the prior art have a width dimension (the basal edge length along one side) of approximately 30 mm. and an overall height (length along its lateral edge which thus includes the thickness of the base member plus the lateral edge length or height of the protective cover) of approximately 34 mm. The width-to-height ratio of the prior art units is thus less than 1.
The reflector component employed in such prior art multiflash units has a height of about 30 mm. and a width (length along one basal or side edge) of about 25 mm. The distance between the apex of the individual reflector elements and the adjacent inner face of the side wall of the protective cover is about 12 mm. in each case. The outer bulb diameter of the flashlamps is about 9 mm., the overall lamp length (bulb length plus the protruding portion of the igniter tube) is about 30 mm., and the bulb volume is about 0.6 cc. The flashlamps are filled with zirconium shreds and gaseous oxygen and the faces of the side walls of the protective cubical cover are flat and smooth. The protective cover is ultrasonically welded to the plastic base member, or the two components can be joined by hot welding or gluing techniques.
Hot welding and gluing techniques provide advantages in that they avoid vibrating the igniter tube assemblies of the percussive flashlamps which inherently occurs during the ultrasonic welding operation and could accidentally ignite the lamps.
Juncture of the plastic cover and base components by hot welding can be achieved by pressing a heated wedge-shaped tool of V or N -- profile against the flash unit in the junction area where the cover and base overlap one another. The localized heating of the plastic produced by the hot tool forms a depression in the plastic at the junction area which has the same shape as the profile of the tool and forms a fusion weld, when the plastic cools, which securely locks the cover and base members together. A multiflash unit having plastic cover and base components that have been heat-welded together in this fashion is disclosed and claimed in U.S. Pat. No. 3,860,810, issued Jan. 14, 1975 to Josef Lukas et al.
Multiflash units of the mechanically-actuable type which are more compact or are "miniaturized" have been proposed and designed. The reduction in size is obtained by decreasing the size of the flashlamps and by making corresponding reductions in the size of the reflector component and plastic base and protective cover components. Specially designed springs for igniting the flashlamps are also employed. The width dimension (basal edge length) of such compact units is only about 24 mm. and their overall height (lateral edge length) is only about 22 mm. Thus, the width-to-height ratio of such compact multiflash units is equal to or only slightly greater than 1. The reflector component employed in such compact units has a height of only about 17 mm. and a width dimension (basal edge length) of only about 22 mm. The spacing between the apex of the individual reflector elements and the inner face of the associated side wall of the protective cover is only about 9 mm. The outer bulb diameter of the flashlamps is about 7 mm., the overall length of the lamps (bulb length plus the protruding portion of the igniter tube) is about 20 mm., and the bulb volume is about 0.2 cc.
Due to the reduction in the height (lateral edge dimension) of the aforementioned compact multiflash units and the corresponding reduction in the height of the reflector component, the shortened individual reflector elements effected an excessive lateral spreading of the light produced by the flashlamps, thereby decreasing the amount of light projected onto the scene being photographed. In order to obtain the desired intensity and distribution of the radiation in the direction in which the picture is being taken, the inner faces of the side walls of the protective plastic cover employed in such compact multiflash units are provided with integrally formed prismatic elements that produce a light-focusing effect. A compact multiflash unit having such integral light-focusing prismatic means is disclosed and claimed in the aforementioned concurrently-filed application Ser. No. 560,463 of Alfred Wacker.
The manufacture of such compact or miniaturized multiflash unit presents a problem in that the percussive flashlamps and their igniter tubes are located much closer to the peripheral rim and junction areas along which the plastic cover and base components are fastened together. Ultrasonically welding the cover and base together is thus impractical since this would vibrate the anvils and accidentally ingite the lamp. When the juncture is formed by hot welding or with a suitable adhesive, the intense heat also might easily accidentally cause the flashlamps to ignite, thus ruining the unit. In addition, such hot welding and gluing techniques inherently distort the integrally-formed inner-prismatic profiling of the side walls of the protective plastic cover and thus impair the quality of the finished multiflash units.